Machine presses for the forming and trimming of intermediate articles into higher level intermediate articles or into finished parts are well known in the prior art. In a trimming operation the article is placed upon a locator die and cutters are pressed upon the article to cut and shear away undesired material from the article. In a forming operation the article to be formed is placed in a lower die and formed by forcing an upper complementary die into the lower die, thereby imparting the desired shape to the article. In both the trimming and the forming process the stresses involved tend to leave the article with a tight friction fit against the principal shaping part of the machine press. This friction fit, or "nesting", as it is sometimes referred to, is a well known phenomenon. Various systems have been devised for removing or ejecting the nested article after a forming or trimming operation.
One known approach for ejecting articles from a press is to provide ejector springs (compression) connected to a pressure pad which is pushed out of the die or trimming area by the trimming or forming operation. When the pressure pad is pushed out of the die or trimming area during closure of the forming or trimming press, energy is stored within the spring. As the forming or trimming stroke is completed the forming or trimming stresses impinged upon the article by the press are removed and the energy stored in the springs force the pressure pad against the article thereby releasing the article from the press. Thus, after the press closure is completed and press opening begins, the pressure pad pushes the article out of the forming or trimming die, as the case may be.
One of the problems with this known ejecting arrangement occurs when the frictional forces of the article against the sides of the cutter blades or the forming die are too great to be dislodged by the energy that is stored in the spring during the trimming or forming stroke. In such cases the article becomes stubbornly nested or lodged within the press and can be quite difficult to remove. When this occurs, an impact from a rubber hammer or similar device is conventionally used to add force in an attempt to dislodge the article. Pressure or a hammer impact on the pressure pad and/or ejector springs may also be attempted; however, these components are often not directly accessible thereby requiring a partial dismantling of the machine in order to remove the stubbornly nested article. All of these steps require extra time and further impose the risk of damaging the trimmed or formed article, the dies involved, and the press itself. It is therefore desirable to provide an ejection system with facilities for dislodging stubbornly nested articles.
Another problem with the spring-and-pressure-pad energy storage ejection system is that in tight quarters, which occur frequently in the press environment, it is difficult to locate the springs which are necessary to provide sufficient ejection force. It will be appreciated that is desirable to provide an energy storage ejection system that is compact and easy to fit into a low clearance location.
Another problem with the ejection of parts by utilizing a compression spring is that the amount of compression of any spring is limited, and accordingly the length of ejection stroke is also limited. When forming or trimming deep drawn parts, a longer ejection stroke is required than can be accommodated only by the compression of the compression spring. It is therefore desired to provide an ejection system easily adaptable to long ejections strokes.
Still another problem of known ejector systems is that ejection of an article occurs typically immediately upon the return of the press to the open position from the closed forming or trimming position. An immediate ejection in many cases would not allow time for the insertion of a tray or other implement to catch the ejected article in order to carry it to the next manufacturing point. Further, immediate ejection often leaves the article displaced from its initial position which, if coupled with inadvertent subsequent closure of the press, will lead to damage of the article and probably also the press dies and cutters. Thus it may be appreciated that it is desirable to provide a press ejection system in which the time of ejection is controllable, and also to provide an ejection system wherein the press is inhibited from closing until the article is successfully ejected from the press.